Earth augers for boring holes in the earth are well known in the art and exemplified by U.S. Pat. No. 4,380,271. This patent describes an auger including a dual flight. Each flight has a leading edge which commences adjacent a pilot bit and a trailing edge which terminates adjacent a chuck. The flights concurrently spiral about a central shaft. A plurality of excavating teeth are arranged in step, radial fashion along the leading edges of the auger flights. During the drilling operations, the cutting teeth cut annular zones of increasing diameter as the auger progresses into the earth.
Various types of teeth useful in earth augers are well known. One type of tooth useful in an earth auger which may be used for rock cutting and drilling is described in U.S. Pat. Nos. 3,924,697 and 3,821,993.
The cutting tooth used in connection with an earth auger typically includes a main body portion terminating in a working end and a shank extending therefrom for insertion into a socket of a holder on the leading edge of the auger. One or more flat style inserts are disposed in the recess and are shaped to form a point.
Another style of digging tooth includes a conical style insert made of a hard wear resistant material mounted within a tooth body secured to auger plates or weld on tooth holders. The cutting teeth are inclined about the body of the auger in the direction of rotation of the auger. As the cutting teeth cut into a work surface, the cutting teeth rotate within the respective block mounts to maintain the sharpness of the cutting tooth insert. It will be appreciated that the conical cutting tooth insert is typically a wear resistant cemented carbide insert having a conical shape. The conical insert utilized on this type of tool is commonly between 0.3 and 0.75 inches in diameter to provide sufficient strength and allow for adequate surface contact with the work surface.
It will also be appreciated that due to the size of the individual cutting teeth and block assemblies, the number of cutting teeth that may be secured to the auger is limited by the size of the cutting tooth and cutting block assemblies mounted on the auger and the distance between the various cutting teeth positioned about the body of the auger. To provide increased cutting tooth action, the tendency in the industry has been to increase the diameter of the conical style insert and decrease the number of cutting teeth mounted about the auger. Although increasing the cutting tooth size and decreasing the number of cutting teeth mounted about the auger has increased the cutting action, it has also decreased the cutting efficiency of the auger. More particularly, as the cutting teeth are brought into contact with a work surface, large areas of the work surface between the cutting teeth are not affected and thus not cut away. The nonremoval of portions of the work surface, such as a rock surface, is known as coring. Coring is recognized as causing excessive wear of the body of the rock auger tooth as well as impeding the penetration of the auger.
Yet another style of rock auger tooth is disclosed in U.S. Pat. Nos. 3,426,860; 3,300,883; 3,136,077 and 2,968,880. The teeth disclosed in U.S. Pat. Nos. 3,426,860; 3,300,883; 3,136,077 and 2,968,880 generally include a tapered distal portion which performs the digging function and a bifurcated proximal portion composed of two prongs separated from each other by a rectangular slot which extends forwardly from the proximal end of the teeth. Each tooth may include a straight transverse cutting edge or a plurality of chisel style carbide inserts having a straight transverse cutting edge. When engaged in a hard work surface such as rock, the transverse chisel style cutting edge has a tendency to grind and pulverize the surface to be cut and resist penetration into the work surface.
Moreover, as disclosed in U.S. Pat. No. 3,426,860, the body of the tooth is formed of a relatively soft material in relation to the hard inserts such that the body of the tooth wears and recedes whereas the hard inserts do not wear rapidly thus shortening the useful life of the tooth body. This problem is exacerbated by the minimal gage between the tip of the chisel style carbide insert and the tooth body such that during cutting of the work surface the tooth body is exposed to the abrasive pulverized cut work surface.
To alleviate the aforementioned problems, such as preventing excessive wear of the body of the tooth and providing a more efficient cutting tooth, we have invented a replaceable digging tooth for an earth auger having a plurality of cutting inserts of a specific shape which possesses sufficient gage clearance to prevent excessive wear of the tooth body and provides superior cutting action.
Accordingly, it is an aspect of the present invention to provide a replaceable digging tooth for an earth auger having a plurality of conical cutting inserts. The replaceable digging teeth in accordance with the present invention may utilize existing known means for holding the digging teeth to existing earth augers for improved economy.
Another aspect of the present invention is to provide a replaceable digging tooth for an earth auger having a plurality of conical cutting inserts which provide maximum rock cutting action by increased cutting pressure.
It is a further aspect of the present invention to provide a replaceable digging tooth for an earth auger having a plurality of conical cutting inserts which provide increased gage distance between the tip of each insert and the tooth body for improved cutting penetration, longer tooth body life and less cutting resistance.
Yet another aspect of the present invention is to provide a replaceable digging tooth for an earth auger having a plurality of conical cutting inserts brazed into individual insert receiving holes to allow for proper gage distance.
Another aspect of the present invention is to provide a digging tooth for an earth auger that has improved penetration in hard rock and improved life and wear properties.
Another aspect of the present invention to provide a replaceable digging tooth for an earth auger having a plurality of conical cutting inserts that is simple and economical to manufacture.